1. Field of the Invention
This invention relates to a clutch release device, and more particularly to a clutch release bearing means of the self-centering type.
2. Description of the Prior Art
Generally, the clutch release device of this type has a clutch release bearing provided for a sleeve mounted for axial sliding movement on a front cover projectedly provided on a transmission means. Either the inner race or the outer race of the bearing is rotatable and the race which is rotatable is caused to bear against a torque transmitting member such as diaphragm spring or pawl of the clutch device to thereby create the release action of the clutch.
However, it is extremely difficult in manufacture and assembly to precisely align the axis of the clutch release bearing with the rotational axis of the fly-wheel. This misalignment is a parallel deviation (eccentricity) between the rotational axis of the fly-wheel and the center line of the bearing of the clutch release device.
This causes abnormal slip of the surface of contact between the torque transmitting member of the clutch device and the clutch release bearing, which slip in turn leads to wear of this contact portion and production of unpleasant abnormal noise or vibration, and further to heaviness of the clutch operation. This is becoming a more and more serious problem today in view of the tendency of automobiles toward higher speeds.
For this reason, there has already been proposed a device in U.S. Pat. No. 3,416,637, in which the clutch release bearing means is mounted with a clearance so as to be movable in a direction perpendicular to the axis of the sleeve and the bearing means is displaced so that the center thereof is aligned with the rotational axis of the fly-wheel by a centripetal force acting on the clutch release bearing means when rotating in contact with the diaphragm, thus fixing the clutch release bearing means with respect to the sleeve at the displaced position by the friction force resulting from the spring force, namely, holding the bearing means at its aligned position by the spring force. However, the conventional device of this type is disadvantageous in that it is apt to produce fretting or creep and when the aforementioned deviation is relatively small, perfect alignment or centering is difficult to obtain.
The conventional device of this type has a further disadvantage that when it is subjected to a shock load after alignment, eccentricity is apt to occur over the full extent of a predetermined clearance.
There has also been proposed a device in U.S. Pat. No. 3,625,327 in which an elastic member is inserted between the clutch release bearing means and the sleeve so that the bearing means is freely displaceable to its aligned position. In this case however, the aligning operation must take place for each clutch release and this not only leads to poor durability of the device but also produces vibration each time the aligning or self-centering operation takes place, and results in serious wear of the diaphragm.